Apparatus for shearing of steel strip end in hot finish rolling

ABSTRACT

Method and apparatus for shearing of front and rear ends of a steel strip by means of two pairs of knives. One of these pairs is just for front end shearing, and the other is for rear end shearing. These knives are provided on the periphery of two drums. Each drum has one knife for front end shearing and one knife for rear end shearing. The positions of the knives on each drum are arranged in such a manner that the knife for front end shearing is lagged not more than 180* behind the knife for rear end shearing in the direction of shearing. The drums are mutually rotated in different directions for the shearing of one end of the steel strip. By virtue of this method, sheared ends of a steel strip may be considerably improved to obtain a good passability through the hot finishing rolls, and the apparatus for shearing may need less power to operate.

United States Patent Noda et a1.

[ July 22, 1975 [75] Inventors: Akira Noda, Nagoya; Atsuhiro Wakako, Handa; Tadashi Kodashima; Akio Tanaka, both of Tokai, all of Japan [73] Assignee: Nippon Steel Corporation, Japan [22] Filed: June 13, 1973 [21] Appl. No.: 369,421

[52] US. Cl 83/345; 83/674 [51] Int. Cl B26d 1/40 [58] Field of Search 83/674, 673, 694, 345, 83/288, 303

[56] References Cited UNITED STATES PATENTS 2,181,879 12/1939 Edgerton 83/345 X 2,221,022 11/1940 Ellis 83/345 X 2,298,877 10/1942 Edwards et a1, 83/288 X 2,665,736 1/1954 Boersma et al.... 83/303 X 3,149,520 9/1964 Fish et a1. 83/288 Primary Examiner-Frank T. Yost Attorney, Agent, or Firm-T0ren, McGeady and Stanger [57] ABSTRACT Method and apparatus for shearing of front and rear ends of a steel strip by means of two pairs of knives. One of these pairs is just for front end shearing, and the other is for rear end shearing. These knives are provided on the periphery of two drums. Each drum has one knife for front end shearing and one knife for rear end shearing. The positions of the knives on each drum are arranged in such a manner that the knife for front end shearing is lagged not more than 180 behind the knife for rear end shearing in the direction of shearing. The drums are mutually rotated in different directions for the shearing of one end of the steel strip. By virtue of this method, sheared ends of a steel strip may be considerably improved to obtain a good passability through the hot finishing rolls, and the apparatus for shearing may need less power to operate.

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oo 00 (D Q (I) (I) D ."J 1 G) C) (I) 00 (D O I! I III@ Q (I) APPARATUS FOR SHEARING OF STEEL STRIP END IN HOT FINISH ROLLING BACKGROUND OF INVENTION In conventional continuous hot rolling, roughly rolled steel strip is subjected to finish rolling after removing front end and rear end irregular portions which were caused by rough rolling. This is carried out for the purpose of improving the passability of the strip in a finish rolling to be performed in succession, for which reason irregular portions are usually removed just before the finishing roll.

Tangible influences upon the passability of irregular portions are represented by the seizing property of a rolling mill for front end portions and by the slippingout property thereof for rear end portions.

When the seizing property and the slipping-out property are compared, even if the degree of irregularity is allowable for the slipping-out property, the irregularity of the same degree cannot be allowed for the seizing property, thus more strict control is required on the seizing property.

Accordingly, the irregular portions of both ends are not always removed, but the fact is that the front end is almost always removed, while the rear end is removed in compliance with its degree.

However, this does not mean that the removal of irregular portions of the rear end is unnecessary.

Nevertheless, up to the present, there has been a tendency that the removal of the irregular portion of the rear end was somehow ignored as compared with that of the irregular portion of the front end.

It is clear from the fact that in the shearing of the strip steel end as mentioned above, a shearing machine is used, wherein a pair of upper and lower drums 3 and 4 each provided with a knife 1 and 2, as shown in FIG. 1, are rotatably supported on frames 6 forming a pass line for steel strip between them as shown in FIG. 2, and gears 7 and 8 which are respectively united with the drums are driven by a motor 12 through a coupling 9, a reduction gear and a coupling 1 1. Thus both the front end and the rear end of the steel strip are sheared and become convex in the direction of rolling as shown in FIG. 3.

Namely, in the usual shearing system, a pair of upper and lower drums are respectively provided with one knife, which knives rotate oppositely and a strip steel is made to run between them. Since the knife edge is formed so as to make a convex sheared form at the front end of a strip steel in the direction of rolling, the sheared form cannot but become convex in the direction of rolling also at the rear end of the same strip steel. Such a form is by no means a favorable one for the passability of the rear end of the strip steel, but is allowable for the passability of the front end.

Of course, with a form as shown in FIG. 3, it is more favorable for the passability than a case when the rear end is not removed. However, a sheared form shown in FIG. 4 is more advantageous to obtain more favorable passability.

To obtain such a sheared form of the rear end which is symmetric with respect to the front end, a knife for shearing the front end and a knife for shearing the rear end must be separately provided, so long as a strip steel is sheared during its progress. For such an object, two systems are considered, one of which is provided with two sets of shearing machines (as shown in FIG. 2) having drums (as shown in FIG. 1), one for shearing of the front end and the other for shearing of the rear end, each used for a single purpose, and the other of which is provided with a shearing machine having upper and lower drums, each incorporating two shearing knives, one for the front end and the other for the rear end, using one machine for a double purpose.

Hereupon, an important matter is not merely to obtain such a sheared form as shown in FIG. 4, but is to be investigated how toobtain the form rationally, and in this point, the former system requires much larger equipment than usual and is quite inconvenient and therefore out of the question.

Also, in the latter system, according to the way the knives are incorporated, the acceleration angle, i.e., the angle from starting position to shearing position, becomes smaller than the usual angle, so that a driving device of large capacity is required to obtain necessary shearing speed. Further, the idle time, i.e., the time needed from a shearing to the next shearing, becomes longer, thus causing a problem that rolling efficiency cannot be improved.

For instance, the drums with two pairs of knives for the latter system are shown in FIG. 5. The knives l, 2 of the upper and lower drums 3, 4 are used exclusively for shearing of the front end, and the knives 1', 2' are used exclusively for shearing of the rear end. The knives 1', 2 are set at intervals of around the axis respectively from the knives 1, 2.

If the shearing is performed by rotating the upper drum 3 in anti-clockwise direction and the lower drum 4 in clockwise direction while the steel strip 5 is travelling to the right, the positions in FIG. 5 correspond to waiting positions of the rear end shearing. When the shearing of the rear end is carried out, the drums 3, 4 are respectively suring back in the opposite direction to the shearing direction, in order that the drums may be accelerated with enough acceleration angle, up to the speed synchronized with the speed of the steel strip.

But the acceleration angle is limited, because the drums can retreat merely in a range where the knives 1, 2 for shearing the front end do not hit against the steel strip 5, so that the maximum retreat positions of the knives become respectively as shown with dotted lines in FIG. 5, and the maximum acceleration angle is shown by a.

In practice, an angle-a becomes smaller because of some allowance, so that the driving device in FIG. 2 which may be used for the drums with one pair of knives in FIG. 1, is not sufficient and reinforcement by means of a driving system including the motor 12 is indispensable.

Further, the positions of the knives accompanied with shearing will be explained by way of FIG. 7, wherein (a) is a waiting position for shearing of the rear end, and for the sake of easy discrimination, only the upper drum 3 is shown and the shearing knife 1' for rear end is shown in black, and the shearing knife 1 for the front end in white.

A strip steel 5 travels to the right.

b. is a starting position of shearing, and the drum will swing back from the position (a) to this position before shearing. (c) is a shearing position, where the shearing is performed by accelerating the drum up to a speed synchronizing with the strip steel within a range of acceleration angle shown by a.

d. is a retardation and stop position after shearing.

e. is a waiting and starting position for shearing of the front end, where the shearing of the rear end is finished by resetting from the position (d) to this position.

The shearing of the front end will start from the position (e).

f. is a shearing position, where the shearing is per formed by accelerating the drum up to a speed synchronizing with the strip steel within a range of acceleration angle shown by a.

g. is a retardation and stop position after shearing.

h. is a waiting position for shearing of the rear end similar to the position (a), where the shearing of the front end is finished by resetting from the position (g) to this position.

In all, one rotation is performed by combining the shearing of the rear end and the shearing of the front end.

Such such shearings may be admitted when both ends of a strip steel are sheared, but otherwise they become quite irrational.

For instance, while in a waiting position for shearing of the rear end shown in FIG. 7 (a), and when the rear end of a strip steel need not be sheared and removed, but the front end of the next strip steel needs to be sheared and removed, the state must become the posi tion (c) after the rear end is passed and rotated via the positions (b), (c) and (d), during which succeeding strip steel cannot be passed. Thus the idle time becomes long and the rolling efficiency is not improved, and what is worse, the power required for the rotation is entirely in vain.

Such a problem may be also caused when the shearing of the rear end is performed at (c) and finished at (d) and while in a waiting position for shearing of the front end at (e), the front end of next strip steel need not be sheared and removed, but the rear end thereof needs to be sheared and removed.

SUMMARY OF THE INVENTION This invention relates to a method for shearing of end portions of a steel strip in a hot finish rolling, having for its object to solve advantageously the above mentioned difficult problems and to provide an improved, rational and efficient method for shearing of a strip steel.

According to one aspect of the invention, respective shearing knives for the front end and the rear end are incorporated around axes of a pair of upper and lower drums, which are driven in different directions, in such a manner that the angle of lag of the shearing knife for the front end relative to the shearing knife for the rear end is confined less than 180 in the direction of rotation of the drum. Thus lach one is passed through a shearing position by the shearing of one end, regardless of shearing for front end or rear end.

Namely, when such as sheared form as shown in FIG. 4 is obtained by a shearing which is caused in such a manner that respective knives for the front end and for the rear end are incorporated with a pair of upper and lower drums, which are driven in different directions, and a strip steel is traveling through a range of opposite rotations of upper and lower knives for shearing of the front end and of the rear end, both of the knives are passed through a shearing position on one shearing, whereupon the drum is set to make one rotation or approximately one rotation for one shearing and the position of the knife when the shearing is finishedis regarded as the position of the knife when the shearing is started.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of rotary drums used in usual method for shearing.

FIG. 2 is a schematic explanatory drawing of a rotary drum shearing machine.

FIG. 3 is an explanatory drawing showing a sheared form obtained by usual method for shearing.

FIG. 4 is an explanatory drawing showing a preferable sheared form.

FIG. 5 is a sectional view of drums incorporated with knives for the front end and the rear end spaced by 180 around the axes.

FIG. 6 shows one embodiment of the apparatus of the present invention.

FIGS. -711 are explanatory drawings showing the process of shearing by means of the drums shown in FIG. 5.

FIGS. 8a-8/1 are explanatory drawings showing an embodiment of the method of the present invention.

FIGS. 9 and 10 show achematically the operation controlling mechanism of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 8a-8h the angle of lag of the shearing knife I for front end shearing from the shearing knife 1' is confined less than The positions (a), (e) and (h), which are spaced 270 from the shearing positions (c) and (f) in the direction opposite to the rotation, are set as the waiting positions, and the drum is rotated by 360 from these positions.

The steps from (a) to (h) are shown respectively corresponding to those in FIGS. 7a-7h i.e., (a) is the waiting position for rear end shearing, (b) the starting position for shearing, (c) the position for shearing, (d) the position for finishing of shearing, (e) the waiting and starting position for front end shearing, (f) the position for shearing and (g) the position for finishing of rear end shearing.

When the front end shearing is performed in succession to the rear end shearing, the steps are as mentioned above, wherein (a) is the waiting position for rear end shearing as well as for front end shearing, so that in case the rear end shearing is not necessary, (a) becomes the starting position for front end shearing as it is.

Similarly, (e) is the waiting position for front end shearing as well as for rear end shearing, and (h) becomes the waiting position of rear end shearing or the waiting and starting position of front end shearing, so that it is no matter how intricately the rear end shearing and the front end shearing may be mixed.

It goes without saying that when the knife for the front end shearing is provided in lagged relation of more than 180 from the knife for the rear end shearing, it becomes more inconvenient than in the case of FIG. 5.

Namely, upon shearing of the end of strip steel in a hot finish rolling, the shearing speed of the front end shearing may be determined relatively free and generally it is determined on a constant speed. However, the shearing speed of the rear end shearing is determined by the rolling schedule because the speed of steel strip is determined by the entrance speed of the finishing mill, and as a shearing machine, a driving power necessary for acceleration up to the maximum speed with the acceleration angle of the rear end shearing is needed. According to this driving power the capacity of a motor and a power source is determined, so that the fact that the acceleration angle of the rear end shearing may be made larger means that the capacity of the motor for driving the shearing machine and of the power source may be made smaller. Thus the acceleration angle a of the rear end shearing from (b) to (c) in FIG. 8 is larger by 90 compared with that in FIG. 7, and the driving power becomes smaller in proportion to that amount.

When the waiting position of the knife for the front end shearing is set as the same position as in FIG. 8 and the angle of lag of the knife for the front end shearing is confined to 60, the acceleration angle of the rear end shearing may be made larger by 30 than in FIG. 8, and further when the angle of lag of the knife for front end shearing is made smaller, the acceleration angle of the rear end shearing may be made larger.

But, if the angle of lag of the knife for front end shearing is made too small, the position of attachment thereof comes close to the position of attachment of the knife for rear end shearing and would weaken the mechanical strength of the drum, so that it is desirable that the angle of lag of the knife for front end shearing not be made smaller than about 60.

On the contrary, when the waiting position of the knife for front end shearing is set as the same position as in FIG. 8 and the angle of lag of the knife for front end shearing is made larger than in FIG. 8, the acceleration angle of the rear end shearing becomes smaller than in FIG. 8. However, if the angle of lag is within about 150, the driving power therefor may be managed with those required in case of the shearing machine in FIG. 2 provided with the drum in FIG. 1 and no reinforcement of the driving system is needed, so that it is desirable that the angle of lag of the knife for front end shearing is preferably less than about 150.

And, in FIG. 8 the position spaced by 270 in the opposite direction to the direction of rotation from the shearing position of the knife for front end shearing is set as the waiting position, and from this standard position the drum is rotated by 360, i.e. just one rotation is performed. However, the waiting position may be set at any place in a range outside of the pass line of strip steel, and the rotation of the drum may be performed within a range before and after 360 (by combining alternately the rotations of a little more and less than 360), provided that both knives rotate passing through the shearing position.

And anyway, it is better to make the acceleration angle of the rear end shearing larger, and it is not necessary to prefer intentionally any unfavorable range, but the smaller the angle of lag of the knife for the front shearing is made, the larger its degree of freedom becomes, so that from such a point of view it is desirable that the angle of lag of the knife for front end shearing should be preferably less than about 150.

For instance, in FIG. 8 the knife position (a) is set as the waiting position for rear end shearing as well as the waiting position for front end shearing, and the knife position (b) is set as the starting position for rear end shearing or for front end shearing, but the fact that the angle of lag of the knife for front end shearing is 90, when it is compared with the case of 180 (FIG. 7), that is, the comparison between mutual waiting positions,

should (a) in FIG. 8 be also compared with (b) in FIG. 8, the acceleration angle of rear end shearing is larger, so that (a) in FIG. 8 may be set as the waiting and starting positions for the rear end shearing and the front end shearing, and in such a case, the steps from (a) to (b), that is, the back swing, may be eliminated and the position may be set directly from (a) to (0).

Of course, the knife position of (b) in FIG. 8 may be set as the waiting and starting positions for the rear end shearing and the front end shearing, and in such a case, the acceleration angle of the rear end shearing may be made larger, and such a knife position may be also obtained by rotating the drum with a little smaller angle than 360.

And, in the present invention, the reason why the knife for front end shearing is rotated lagging behind the knife for rear end shearing, is that in case of the rear end shearing, the strip steel has passed through the waiting state and the knife for rear end shearing surely needs to contact with the strip steel firstly under the shearing state.

In case of the front end shearing, the strip steel has not yet arrived under the waiting state, but after the knife for rear end shearing has passed the shearing position, the strip steel will arrive, which will then be sheared by the knife for front end shearing.

Next explanation will be made on the operation of the apparatus of the present invention by referring to FIG. 9.

In FIG. 9, 20 is a detector for detecting the front and rear ends of the steel strip 5, and an optical detector called HMD is usually used. 21 is a speed detector for synchronizing the speed of the drum shear with the speed of the steel strip at the time of shearing the front end, and usually a taco-generator called a measuring roll is used and is connected to a roll rotating in contact with the steel strip. 22 is a speed detector which functions in a similar way as the speed detector 21 at the time of shearing the rear end and is provided behind the drum shear. 24 is an angle detector for detecting the angle of the drum, connected to the drum shaft and actuated by a rotary limit switch. 27 is a tacogenerator, 28 is a braker, both being connected to a driving motor. 30 is a controlling device, whose functions will be explained referring to FIG. 10.

In FIG. 10, which shows the flow of controlling signals, 23 is a starting time operating device, which receives signals of the rear end of the steel strip from the detector 20 and signals of the strip speed through the detector 21 in case of the front end shearing or through the detector 22 in case of the rear end shearing and operates for optimum starting time of the drum shear for shearing the moving strip end portion. A controlling device similar to ones used in a conventional shearing machine may be used. However, it will be understood that the angle conditions between the two knives in case of the shearing of the rear end is taken into the operating conditions in the present invention. 25 is an operation instruction device, which receives the starting instruction from the operation device 23 and as the drum rotation proceeds gives instructions for an operation mode predetermined by the rotary limit switch corresponding to the signal from the drum angle detecting device, namely in correspondence to the drum angle. 26 is a controlling device for controlling the motor speed, which controls the motor in accordance with an instruction from the operation instruction device 25, and receives speed feed-back from the tacogenerator 27 in order to synchronize the drum rotation and the shearing. Signals from 21 and 22 provide a speed standard for synchronizing the drum speed with the strip speed at the time of shearing both the front and the rear end. A conventional device as used in a conventional shearing machine may be used for the controlling device 26.

The key point of the present apparatus is the connection of the drum 3 with the angle detection device 24. As described hereinbefore in connection with FIGS. 6 and 8, in the conventional shearing method, two cycles of shearing operation from the starting to the stopping is effected while the drum 3 makes one rotation. Whereas according to the shearing according to the present invention, only one cycle of shearing operation from the starting and the stopping is effected while the drum 3 makes one rotation. This means that in the conventional shearing method an operation instruction of two cycles per one rotation of the drum is given while in the present invention an operation instruction of one cycle per one rotation of the drum is given.

By taking the above-mentioned steps, the following merits are gained;

1. the driving power of a shearing machine may be made small, for instance, the angle of lag of the knife for front end shearing is made 90, a position spaced by 285 in the opposite direction of rotation from the shearing position is set as the starting position for shearing, the drum is rotated by one rotation, and a low carbon steel plate, which has 32 mm thickness and 850 mm width with 1050C in temperature after the rough rolling is finished, is sheared at its rear end with a maximum shearing speed of 380 fpm without back swing, and the operation may be performed with only one set of a motor of 205/410 KW.

If the above-mentioned shearing is performed according to the method shown in FIG. 7, setting a position, where the knife for front end shearing was swung back up to the same position as above-mentioned, as the starting position for shearing, two sets motor will be needed.

2. When the angle of lag of the knife for front end shearing is suitably selected in connection with the driving power, the back swing may be eliminated, thus eliminating the danger of contact between strip steel and the knife due to the back swing, so that any damage by the knife, scratches on strip steel and the like will not be caused.

3. In case the waiting position and starting position for rear end shearing and for front end shearing are set in common, the control device becomes simple.

4. In case the rear end shearing is not performed, the step of idle of rear end shearing becomes useless, and idle time may be shortened; and the like are obtained, thus the shearing with good passability may be performed.

We claim:

1. An apparatus for shearing end portions of strip steel in a hot finish rolling comprising an upper drum, a lower drum mounted parallel with said upper drum so as to form a pass line therebetween for the strip steel, each of said drums having on its periphery only two knives, a first knife for front end shearing, and a second knife for rear end shearing, said first knife lying at a lag angle measured in the direction of shearing rotation from said second knife in the range of 60 and means for rotating said drums in opposite direction relative to one another, the periphery of said drums from said first knife to said second knife in a direction opposite to that for said lag angle being continuous and uninterrupted. 

1. An apparatus for shearing end portions of strip steel in a hot finish rolling comprising an upper drum, a lower drum mounted parallel with said upper drum so as to form a pass line therebetween for the strip steel, each of said drums having on its periphery only two knives, a first knife for front end shearing, and a second knife for rear end shearing, said first knife lying at a lag angle measured in the direction of shearing rotation from said second knife in the range of 60* 150*, and means for rotating said drums in opposite direction relative to one another, the periphery of said drums from said first knife to said second knife in a direction opposite to that for said lag angle being continuous and uninterrupted. 